Best Chocolate Birthday Cake

Ingredients (9)

• + 1 (18.25 ounce) package devil's food cake mix add to pantry
• + 1 (3.9 ounce) package instant chocolate pudding mix add to pantry
• + 1 cup sour cream add to pantry
• + ¾ cup vegetable oil add to pantry
• + ¾ cup water add to pantry
• ✓ 4 eggs
• ✓ 1 cup semisweet chocolate chips
• + 1 (16 ounce) package prepared chocolate frosting add to pantry
• + 2 tablespoons candy-coated milk chocolate pieces (such as M&M's®), or as desired add to pantry